Recently, by the use of for instance advanced semiconductor machining technology, field emission cold cathodes have been under active study and have been forwarded to apply in flat panel displays. A flat panel display comprises a rear plate in which a lot of field emission electron emitters are formed as electron sources on a substrate, and a face plate formed of a glass substrate or the like thereon a phosphor layer is formed. These are oppositely disposed to each other a prescribed gap apart. Such flat panel displays, different from liquid crystal displays, are self-emitting and can dispense with a backlight. Accordingly, on the basis of these, the flat panel displays are characterized in being lower in power consumption, broader of an angle of sight, and higher in response speed.
In the flat panel display using an electron emitter, a volume of a vacuum vessel formed of the rear plate, the face plate and support frames is remarkably smaller in comparison with that of an ordinary CRT. Despite the above, an area of wall surface releasing gas does not decrease. As a result, when an amount of gas comparable with that of the CRT is released, a pressure increase in the vacuum vessel becomes extremely high. From the above circumstances, getter material plays a particularly important role in the flat panel display. However, the getter material, being electrically conductive, from a point of view of preventing short-circuit of wiring or the like, is restricted in positions to deposit.
To the aforementioned points, it is proposed that the getter material is disposed in the periphery of the vacuum vessel and a getter film is formed in the periphery that does not adversely affect on an image display area (cf. Japanese Patent Publication Nos. HEI 5-151916 JP-A, HEI 4-289640 JP-A or the like). However, in such method of disposing the getter film, the getter film formed at the periphery cannot effectively absorb gases released in the image display area. Accordingly, a high vacuum in the vacuum vessel cannot be maintained over a long period.
From the aforementioned circumstances, it is under study to deposit the getter film in the image display area. For instance Japanese Patent Publication No. HEI 9-82245 JP-A discloses as follows. That is, getter material formed of Ti, Zr or alloys thereof is deposited on a metal back formed on the phosphor layer of the faceplate in one way. In another way, the metal back itself is formed of one the aforementioned getter materials. In still another way, in the image display area, the getter material is deposited in portions other than that of electron emitters of the rear plate.
However, in the flat panel display disclosed in the aforementioned Japanese Patent Publication No. HEI 9-82245 JP-A, the getter material is deposited in the ordinary panel process. As a result, the getter material is inevitably oxidized in its surface. Since the getter material is particularly important of its degree of surface activity, the getter material oxidized in its surface cannot exhibit a satisfying gas adsorption effect.
Accordingly, in the aforementioned gazette, it is disclosed that a space between the face plate and the rear plate is hermetically sealed through the support frame to form a vacuum vessel, thereafter an electron beam or the like being irradiated on the getter material to activate. However, such method cannot effectively activate the getter material. In particular, when the getter material is activated after the formation of the vacuum vessel, gaseous components such as oxygen or the like liberated in the process of activation stick to the electron emitter and the other member. As a result, at this stage, electron emission characteristics or the like are liable to deteriorate.
Furthermore, the getter materials made of Ti, Zr or the alloys of which the aforementioned Japanese Patent Publication No. HEI 9-82245 JP-A official gazette mainly describe have problems that function thereof itself is low. Accordingly, in the flat panel displays operating in the neighborhood of room temperature or at a little higher temperature than that, a sufficient getter function cannot be obtained.
In the aforementioned official gazette, it is disclosed that, as the getter material, evaporable getter materials such as alloys essentially consisting of Ba can be applicable. However, since the evaporable getter materials are assumed to use as alloy, in the flat panel display that operates in the neighborhood of room temperature or at a little higher temperature than that, sufficient gettering action may not be obtained. Furthermore, if the Ba were evaporated to deposit itself as a Ba film, it would be extremely difficult to suppress the getter film from sticking onto unnecessary portions. As a result, short-circuit of wiring or the like is liable to occur.
For instance a reinforcing plate is ordinarily disposed between the faceplate and the rear plate. When the getter material sticks onto such reinforcing plate, there may occur short-circuiting between an electron emitter on a cathode side and a phosphor layer on an anode side to result in an occurrence of broken driver or lighting failure. Accordingly, the aforementioned official gazette states that, when employing the evaporable getter, in order to prevent the wiring from short-circuiting, a device is necessary that restricts a direction into which vapor of the getter material sputters. However, for that, a particular configuration is required to result in a complication.
When the evaporable getter film consisting of an alloy film or the like of which primary component is Ba is formed in the course of ordinary panel process, the getter film (Ba alloy film) is oxidized more rigorously than the getter material consisting of Ti, Zr or alloys thereof is. Accordingly, it is far from exhibiting function as the getter film.
The object of the present invention is to provide a method for manufacturing a flat panel display and a flat panel display itself. Here, in the method for manufacturing the flat panel display, an evaporable getter film of excellent getter function, while maintaining activity, is deposited in an image display area in a vacuum vessel, thereby, the inside of the vacuum vessel is enabled to be a high vacuum with good reproducibility. The flat panel display enables the inside of the vacuum vessel to maintain a high vacuum.